The present invention pertains to support bases of vibrators that are used as seismic signal generators. More particularly, this invention is directed to a shear wave seismic signal generator with a support base that can be used on a hard surface and which is self-expanding in response to slippage on that surface to achieve a more stable position.
Vibrational devices that are used as seismic signal generators (particularly shear wave generators) are often equipped with bases that have spikes, inverted cones, or the like, positioned on the ground-engaging surface to penetrate the surface of the ground to insure positive (i.e., non-slipping) engagement between the generator and the ground. These generators do significant damage to the surface of the ground. Accordingly, such generators cannot be used where such damage cannot be tolerated, e.g., on pavement or other similar hard surfaces. If a patterned seismic array is taken in the vicinity of such a surface, the inability of existing generators to transmit a signal through such a surface can produce a hole in the data or otherwise render the information obtained from the seismic testing incomplete.
It is an object of the present invention to provide a seismic signal generator that can be utilized on paved or other hard surfaces. It is yet a further object to provide such a generator that is capable of self adjustment should slippage occur in order to achieve a more stable footing.
These and other objects of the present invention are accomplished by replacing the solid vibrator support base typical of such generators with a pair of tread members. These tread members are interconnected to the vibrator3 s reaction mass by means which permits lateral translational movement by the treads with respect to the reaction mass. The treads can slide (translate) on guide rods and after placement under load, the treads are biased outwardly away from the reaction mass by 2000-3000 psi hydraulic fluid. If the initial positioning of the treads is unstable (i.e., if any slippage is incurred), the hydraulic fluid will hold the tread in the outer position to which it has slipped. This process continues until the most stable condition possible is achieved by the treads insuring optimum contact between the signal generator and the surface of the ground for maximum signal transfer.
Various other characteristics, features and objectives of the present invention will become apparent after a reading of the following specification.